From National Geographic online, we have a brief article by Glenn Hodges and some splendid photos by Paul Nicklen of emperor penguins (Aptenodytes forsteri), the largest and most stately species of the Sphenisciformes.
Here are some of Nicklen’s photos (and Hodges’s text, indented; captions are from the article:
Note the bubbles. As Hodges reports, these may be key to understanding why they can swim so fast, not only to catch prey but also to make that hasty exist from the water:
With the help of Poul Larsen, a mechanical engineer at the Technical University of Denmark, they analyzed hours of underwater footage and discovered that the penguins were doing something that engineers had long tried to do with boats and torpedoes: They were using air as a lubricant to cut drag and increase speed.
When an emperor penguin swims through the water, it is slowed by the friction between its body and the water, keeping its maximum speed somewhere between four and nine feet a second. But in short bursts the penguin can double or even triple its speed by releasing air from its feathers in the form of tiny bubbles. These reduce the density and viscosity of the water around the penguin’s body, cutting drag and enabling the bird to reach speeds that would otherwise be impossible. (As an added benefit, the extra speed helps the penguins avoid predators such as leopard seals.)
The key to this talent is in the penguin’s feathers. Like other birds, emperors have the capacity to fluff their feathers and insulate their bodies with a layer of air. But whereas most birds have rows of feathers with bare skin between them, emperor penguins have a dense, uniform coat of feathers. And because the bases of their feathers include tiny filaments—just 20 microns in diameter, less than half the width of a thin human hair—air is trapped in a fine, downy mesh and released as microbubbles so tiny that they form a lubricating coat on the feather surface.
Here’s a video taken by Nicklen showing how they can release bubbles to speed up:
If you haven’t seen the movie “March of the Penguins,” I recommend it highly.
And I find this picture mesmerizing; they almost look like ctenophores in the background:
It is my dream to see these in the wild one day (a dream second only to petting a tiger cub). Can someone get me a gig as a lecturer on a Lindblad tour?